Development of olfactory epithelium in the human fetus:Scanning electron microscopic observations

摘要

Aims: Human olfactory epithelium becomes functional atbirth, but prenatal development remains unclear. In the presentstudy, we aimed to clarify the development of human olfactoryepithelium using scanning electron microscopy (SEM). Methods: The development of human olfactory epithelium wasobserved in 24 externally normal fetuses, which were formalin-fixed and long-preserved, with a crown-rump length (CRL) of102-336 mm (gestational week 14-38). The olfactory mucosa inthe superior wall of the nasal septum near the choana weredissected and observed under SEM. We examined the numberof olfactory vesicles per unit area, diameter of olfactory vesicles;and number and length of cilia on olfactory vesicles. Results: At circa (ca) CRL 100 mm (ca 14 weeks), olfactoryepithelium displayed several olfactory vesicles with 1-2 shortcilia per unit area. At ca CRL 150 mm (ca 18 weeks), olfactoryvesicles were present in small clusters, and cilia were longer.At CRL lager than 225 mm (ca 26 weeks), olfactory vesiclesbecame located separately from each other, while length andnumber of cilia per olfactory vesicle were further increased. Conclusion: The present findings suggest that fetal olfactoryepithelium becomes morphologically almost the same as that inadults in late gestation, much later than previously thought.